#!/usr/bin/env python3.7
# vim:fileencoding=utf-8
from __future__ import absolute_import, division, print_function, unicode_literals

__license__ = 'GPL v3'
__copyright__ = '2013, Kovid Goyal <kovid at kovidgoyal.net>'

import itertools, operator, os, math
from threading import Event, Thread
from functools import wraps
from textwrap import wrap

from PyQt5.Qt import (
    QListView, QSize, QStyledItemDelegate, QModelIndex, Qt, QImage, pyqtSignal,
    QTimer, QColor, QItemSelection, QPixmap, QApplication,
    QMimeData, QUrl, QDrag, QPoint, QPainter, QRect, pyqtProperty, QEvent,
    QPropertyAnimation, QEasingCurve, pyqtSlot, QHelpEvent, QAbstractItemView,
    QStyleOptionViewItem, QToolTip, QByteArray, QBuffer, qRed, qGreen,
    qBlue, QItemSelectionModel, QIcon, QFont, QTableView, QTreeView)

from calibre import fit_image, prints, prepare_string_for_xml, human_readable
from calibre.constants import DEBUG, config_dir, islinux
from calibre.gui2.pin_columns import PinContainer
from calibre.ebooks.metadata import fmt_sidx, rating_to_stars
from calibre.utils import join_with_timeout
from calibre.gui2 import gprefs, config, rating_font, empty_index
from calibre.gui2.gestures import GestureManager
from calibre.gui2.library.caches import CoverCache, ThumbnailCache
from calibre.utils.config import prefs, tweaks
from polyglot.builtins import itervalues, unicode_type, range
from polyglot.queue import LifoQueue

CM_TO_INCH = 0.393701
CACHE_FORMAT = 'PPM'


def auto_height(widget):
    # On some broken systems, availableGeometry() returns tiny values, we need
    # a value of at least 1000 for 200 DPI systems.
    return max(1000, QApplication.instance().desktop().availableGeometry(widget).height()) / 5.0


class EncodeError(ValueError):
    pass


def handle_enter_press(self, ev, special_action=None, has_edit_cell=True):
    if ev.key() in (Qt.Key_Enter, Qt.Key_Return):
        mods = ev.modifiers()
        if mods & Qt.CTRL or mods & Qt.ALT or mods & Qt.SHIFT or mods & Qt.META:
            return
        if self.state() != self.EditingState and self.hasFocus() and self.currentIndex().isValid():
            from calibre.gui2.ui import get_gui
            ev.ignore()
            tweak = tweaks['enter_key_behavior']
            gui = get_gui()
            if tweak == 'edit_cell':
                if has_edit_cell:
                    self.edit(self.currentIndex(), self.EditKeyPressed, ev)
                else:
                    gui.iactions['Edit Metadata'].edit_metadata(False)
            elif tweak == 'edit_metadata':
                gui.iactions['Edit Metadata'].edit_metadata(False)
            elif tweak == 'do_nothing':
                pass
            else:
                if special_action is not None:
                    special_action(self.currentIndex())
                gui.iactions['View'].view_triggered(self.currentIndex())
            return True


def image_to_data(image):  # {{{
    ba = QByteArray()
    buf = QBuffer(ba)
    buf.open(QBuffer.WriteOnly)
    if not image.save(buf, CACHE_FORMAT):
        raise EncodeError('Failed to encode thumbnail')
    ret = ba.data()
    buf.close()
    return ret
# }}}

# Drag 'n Drop {{{


def qt_item_view_base_class(self):
    for q in (QTableView, QListView, QTreeView):
        if isinstance(self, q):
            return q
    return QAbstractItemView


def dragMoveEvent(self, event):
    event.acceptProposedAction()


def event_has_mods(self, event=None):
    mods = event.modifiers() if event is not None else \
            QApplication.keyboardModifiers()
    return mods & Qt.ControlModifier or mods & Qt.ShiftModifier


def mousePressEvent(self, event):
    ep = event.pos()
    if self.indexAt(ep) in self.selectionModel().selectedIndexes() and \
            event.button() == Qt.LeftButton and not self.event_has_mods():
        self.drag_start_pos = ep
    if hasattr(self, 'handle_mouse_press_event'):
        return self.handle_mouse_press_event(event)
    return qt_item_view_base_class(self).mousePressEvent(self, event)


def drag_icon(self, cover, multiple):
    cover = cover.scaledToHeight(120, Qt.SmoothTransformation)
    if multiple:
        base_width = cover.width()
        base_height = cover.height()
        base = QImage(base_width+21, base_height+21,
                QImage.Format_ARGB32_Premultiplied)
        base.fill(QColor(255, 255, 255, 0).rgba())
        p = QPainter(base)
        rect = QRect(20, 0, base_width, base_height)
        p.fillRect(rect, QColor('white'))
        p.drawRect(rect)
        rect.moveLeft(10)
        rect.moveTop(10)
        p.fillRect(rect, QColor('white'))
        p.drawRect(rect)
        rect.moveLeft(0)
        rect.moveTop(20)
        p.fillRect(rect, QColor('white'))
        p.save()
        p.setCompositionMode(p.CompositionMode_SourceAtop)
        p.drawImage(rect.topLeft(), cover)
        p.restore()
        p.drawRect(rect)
        p.end()
        cover = base
    return QPixmap.fromImage(cover)


def drag_data(self):
    m = self.model()
    db = m.db
    selected = self.get_selected_ids()
    ids = ' '.join(map(str, selected))
    md = QMimeData()
    md.setData('application/calibre+from_library', ids.encode('utf-8'))
    fmt = prefs['output_format']

    def url_for_id(i):
        try:
            ans = db.format_path(i, fmt, index_is_id=True)
        except:
            ans = None
        if ans is None:
            fmts = db.formats(i, index_is_id=True)
            if fmts:
                fmts = fmts.split(',')
            else:
                fmts = []
            for f in fmts:
                try:
                    ans = db.format_path(i, f, index_is_id=True)
                except:
                    ans = None
        if ans is None:
            ans = db.abspath(i, index_is_id=True)
        return QUrl.fromLocalFile(ans)

    md.setUrls([url_for_id(i) for i in selected])
    drag = QDrag(self)
    col = self.selectionModel().currentIndex().column()
    try:
        md.column_name = self.column_map[col]
    except AttributeError:
        md.column_name = 'title'
    drag.setMimeData(md)
    cover = self.drag_icon(m.cover(self.currentIndex().row()),
            len(selected) > 1)
    drag.setHotSpot(QPoint(-15, -15))
    drag.setPixmap(cover)
    return drag


def mouseMoveEvent(self, event):
    if not self.drag_allowed:
        return
    if self.drag_start_pos is None:
        return qt_item_view_base_class(self).mouseMoveEvent(self, event)

    if self.event_has_mods():
        self.drag_start_pos = None
        return

    if not (event.buttons() & Qt.LeftButton) or \
            (event.pos() - self.drag_start_pos).manhattanLength() \
                    < QApplication.startDragDistance():
        return

    index = self.indexAt(event.pos())
    if not index.isValid():
        return
    drag = self.drag_data()
    drag.exec_(Qt.CopyAction)
    self.drag_start_pos = None


def dnd_merge_ok(md):
    return md.hasFormat('application/calibre+from_library') and gprefs['dnd_merge']


def dragEnterEvent(self, event):
    if int(event.possibleActions() & Qt.CopyAction) + \
        int(event.possibleActions() & Qt.MoveAction) == 0:
        return
    paths = self.paths_from_event(event)
    md = event.mimeData()

    if paths or dnd_merge_ok(md):
        event.acceptProposedAction()


def dropEvent(self, event):
    md = event.mimeData()
    if dnd_merge_ok(md):
        ids = set(map(int, bytes(md.data('application/calibre+from_library')).decode('utf-8').split(' ')))
        row = self.indexAt(event.pos()).row()
        if row > -1 and ids:
            book_id = self.model().id(row)
            if book_id and book_id not in ids:
                self.books_dropped.emit({book_id: ids})
                event.setDropAction(Qt.CopyAction)
                event.accept()
        return
    paths = self.paths_from_event(event)
    event.setDropAction(Qt.CopyAction)
    event.accept()
    self.files_dropped.emit(paths)


def paths_from_event(self, event):
    '''
    Accept a drop event and return a list of paths that can be read from
    and represent files with extensions.
    '''
    md = event.mimeData()
    if md.hasFormat('text/uri-list') and not \
            md.hasFormat('application/calibre+from_library'):
        urls = [unicode_type(u.toLocalFile()) for u in md.urls()]
        return [u for u in urls if os.path.splitext(u)[1] and os.path.exists(u)]


def setup_dnd_interface(cls_or_self):
    if isinstance(cls_or_self, type):
        cls = cls_or_self
        fmap = globals()
        for x in (
            'dragMoveEvent', 'event_has_mods', 'mousePressEvent', 'mouseMoveEvent',
            'drag_data', 'drag_icon', 'dragEnterEvent', 'dropEvent', 'paths_from_event'):
            func = fmap[x]
            setattr(cls, x, func)
        return cls
    else:
        self = cls_or_self
        self.drag_allowed = True
        self.drag_start_pos = None
        self.setDragEnabled(True)
        self.setDragDropOverwriteMode(False)
        self.setDragDropMode(self.DragDrop)
# }}}

# Manage slave views {{{


def sync(func):
    @wraps(func)
    def ans(self, *args, **kwargs):
        if self.break_link or self.current_view is self.main_view:
            return
        with self:
            return func(self, *args, **kwargs)
    return ans


class AlternateViews(object):

    def __init__(self, main_view):
        self.views = {None:main_view}
        self.stack_positions = {None:0}
        self.current_view = self.main_view = main_view
        self.stack = None
        self.break_link = False
        self.main_connected = False
        self.current_book_state = None

    def set_stack(self, stack):
        self.stack = stack
        pin_container = PinContainer(self.main_view, stack)
        self.stack.addWidget(pin_container)
        return pin_container

    def add_view(self, key, view):
        self.views[key] = view
        self.stack_positions[key] = self.stack.count()
        self.stack.addWidget(view)
        self.stack.setCurrentIndex(0)
        view.setModel(self.main_view._model)
        view.selectionModel().currentChanged.connect(self.slave_current_changed)
        view.selectionModel().selectionChanged.connect(self.slave_selection_changed)
        view.files_dropped.connect(self.main_view.files_dropped)
        view.books_dropped.connect(self.main_view.books_dropped)

    def show_view(self, key=None):
        view = self.views[key]
        if view is self.current_view:
            return
        self.stack.setCurrentIndex(self.stack_positions[key])
        self.current_view = view
        if view is not self.main_view:
            self.main_current_changed(self.main_view.currentIndex())
            self.main_selection_changed()
            view.shown()
            if not self.main_connected:
                self.main_connected = True
                self.main_view.selectionModel().currentChanged.connect(self.main_current_changed)
                self.main_view.selectionModel().selectionChanged.connect(self.main_selection_changed)
            view.setFocus(Qt.OtherFocusReason)

    def set_database(self, db, stage=0):
        for view in itervalues(self.views):
            if view is not self.main_view:
                view.set_database(db, stage=stage)

    def __enter__(self):
        self.break_link = True

    def __exit__(self, *args):
        self.break_link = False

    @sync
    def slave_current_changed(self, current, *args):
        self.main_view.set_current_row(current.row(), for_sync=True)

    @sync
    def slave_selection_changed(self, *args):
        rows = {r.row() for r in self.current_view.selectionModel().selectedIndexes()}
        self.main_view.select_rows(rows, using_ids=False, change_current=False, scroll=False)

    @sync
    def main_current_changed(self, current, *args):
        self.current_view.set_current_row(current.row())

    @sync
    def main_selection_changed(self, *args):
        rows = {r.row() for r in self.main_view.selectionModel().selectedIndexes()}
        self.current_view.select_rows(rows)

    def set_context_menu(self, menu):
        for view in itervalues(self.views):
            if view is not self.main_view:
                view.set_context_menu(menu)

    def save_current_book_state(self):
        self.current_book_state = self.current_view, self.current_view.current_book_state()

    def restore_current_book_state(self):
        if self.current_book_state is not None:
            if self.current_book_state[0] is self.current_view:
                self.current_view.restore_current_book_state(self.current_book_state[1])
            self.current_book_state = None

    def marked_changed(self, old_marked, current_marked):
        if self.current_view is not self.main_view:
            self.current_view.marked_changed(old_marked, current_marked)
# }}}

# Rendering of covers {{{


class CoverDelegate(QStyledItemDelegate):

    MARGIN = 4
    TOP, LEFT, RIGHT, BOTTOM = object(), object(), object(), object()

    @pyqtProperty(float)
    def animated_size(self):
        return self._animated_size

    @animated_size.setter
    def animated_size(self, val):
        self._animated_size = val

    def __init__(self, parent):
        super(CoverDelegate, self).__init__(parent)
        self._animated_size = 1.0
        self.animation = QPropertyAnimation(self, b'animated_size', self)
        self.animation.setEasingCurve(QEasingCurve.OutInCirc)
        self.animation.setDuration(500)
        self.set_dimensions()
        self.cover_cache = CoverCache()
        self.render_queue = LifoQueue()
        self.animating = None
        self.highlight_color = QColor(Qt.white)
        self.rating_font = QFont(rating_font())

    def set_dimensions(self):
        width = self.original_width = gprefs['cover_grid_width']
        height = self.original_height = gprefs['cover_grid_height']
        self.original_show_title = show_title = gprefs['cover_grid_show_title']
        self.original_show_emblems = gprefs['show_emblems']
        self.orginal_emblem_size = gprefs['emblem_size']
        self.orginal_emblem_position = gprefs['emblem_position']
        self.emblem_size = gprefs['emblem_size'] if self.original_show_emblems else 0
        try:
            self.gutter_position = getattr(self, self.orginal_emblem_position.upper())
        except Exception:
            self.gutter_position = self.TOP

        if height < 0.1:
            height = auto_height(self.parent())
        else:
            height *= self.parent().logicalDpiY() * CM_TO_INCH

        if width < 0.1:
            width = 0.75 * height
        else:
            width *= self.parent().logicalDpiX() * CM_TO_INCH
        self.cover_size = QSize(width, height)
        self.title_height = 0
        if show_title:
            f = self.parent().font()
            sz = f.pixelSize()
            if sz < 5:
                sz = f.pointSize() * self.parent().logicalDpiY() / 72.0
            self.title_height = max(25, sz + 10)
        self.item_size = self.cover_size + QSize(2 * self.MARGIN, (2 * self.MARGIN) + self.title_height)
        if self.emblem_size > 0:
            extra = self.emblem_size + self.MARGIN
            self.item_size += QSize(extra, 0) if self.gutter_position in (self.LEFT, self.RIGHT) else QSize(0, extra)
        self.calculate_spacing()
        self.animation.setStartValue(1.0)
        self.animation.setKeyValueAt(0.5, 0.5)
        self.animation.setEndValue(1.0)

    def calculate_spacing(self):
        spc = self.original_spacing = gprefs['cover_grid_spacing']
        if spc < 0.01:
            self.spacing = max(10, min(50, int(0.1 * self.original_width)))
        else:
            self.spacing = self.parent().logicalDpiX() * CM_TO_INCH * spc

    def sizeHint(self, option, index):
        return self.item_size

    def render_field(self, db, book_id):
        is_stars = False
        try:
            field = db.pref('field_under_covers_in_grid', 'title')
            if field == 'size':
                ans = human_readable(db.field_for(field, book_id, default_value=0))
            else:
                mi = db.get_proxy_metadata(book_id)
                display_name, ans, val, fm = mi.format_field_extended(field)
                if fm and fm['datatype'] == 'rating':
                    ans = rating_to_stars(val, fm['display'].get('allow_half_stars', False))
                    is_stars = True
            return ('' if ans is None else unicode_type(ans)), is_stars
        except Exception:
            if DEBUG:
                import traceback
                traceback.print_exc()
        return '', is_stars

    def render_emblem(self, book_id, rule, rule_index, cache, mi, db, formatter, template_cache):
        ans = cache[book_id].get(rule, False)
        if ans is not False:
            return ans, mi
        ans = None
        if mi is None:
            mi = db.get_proxy_metadata(book_id)
        ans = formatter.safe_format(rule, mi, '', mi, column_name='cover_grid%d' % rule_index, template_cache=template_cache) or None
        cache[book_id][rule] = ans
        return ans, mi

    def cached_emblem(self, cache, name, raw_icon=None):
        ans = cache.get(name, False)
        if ans is not False:
            return ans
        sz = self.emblem_size
        ans = None
        if raw_icon is not None:
            ans = raw_icon.pixmap(sz, sz)
        elif name == ':ondevice':
            ans = QIcon(I('ok.png')).pixmap(sz, sz)
        elif name:
            pmap = QIcon(os.path.join(config_dir, 'cc_icons', name)).pixmap(sz, sz)
            if not pmap.isNull():
                ans = pmap
        cache[name] = ans
        return ans

    def paint(self, painter, option, index):
        QStyledItemDelegate.paint(self, painter, option, empty_index)  # draw the hover and selection highlights
        m = index.model()
        db = m.db
        try:
            book_id = db.id(index.row())
        except (ValueError, IndexError, KeyError):
            return
        if book_id in m.ids_to_highlight_set:
            painter.save()
            try:
                painter.setPen(self.highlight_color)
                painter.setRenderHint(QPainter.Antialiasing, True)
                painter.drawRoundedRect(option.rect, 10, 10, Qt.RelativeSize)
            finally:
                painter.restore()
        marked = db.data.get_marked(book_id)
        db = db.new_api
        cdata = self.cover_cache[book_id]
        device_connected = self.parent().gui.device_connected is not None
        on_device = device_connected and db.field_for('ondevice', book_id)

        emblem_rules = db.pref('cover_grid_icon_rules', default=())
        emblems = []
        if self.emblem_size > 0:
            mi = None
            for i, (kind, column, rule) in enumerate(emblem_rules):
                icon_name, mi = self.render_emblem(book_id, rule, i, m.cover_grid_emblem_cache, mi, db, m.formatter, m.cover_grid_template_cache)
                if icon_name is not None:
                    pixmap = self.cached_emblem(m.cover_grid_bitmap_cache, icon_name)
                    if pixmap is not None:
                        emblems.append(pixmap)
            if marked:
                emblems.insert(0, self.cached_emblem(m.cover_grid_bitmap_cache, ':marked', m.marked_icon))
            if on_device:
                emblems.insert(0, self.cached_emblem(m.cover_grid_bitmap_cache, ':ondevice'))

        painter.save()
        right_adjust = 0
        try:
            rect = option.rect
            rect.adjust(self.MARGIN, self.MARGIN, -self.MARGIN, -self.MARGIN)
            if self.emblem_size > 0:
                self.paint_emblems(painter, rect, emblems)
            orect = QRect(rect)
            trect = QRect(rect)
            if self.title_height != 0:
                rect.setBottom(rect.bottom() - self.title_height)
                trect.setTop(trect.bottom() - self.title_height + 5)
            if cdata is None or cdata is False:
                title = db.field_for('title', book_id, default_value='')
                authors = ' & '.join(db.field_for('authors', book_id, default_value=()))
                painter.setRenderHint(QPainter.TextAntialiasing, True)
                painter.drawText(rect, Qt.AlignCenter|Qt.TextWordWrap, '%s\n\n%s' % (title, authors))
                if cdata is False:
                    self.render_queue.put(book_id)
                if self.title_height != 0:
                    self.paint_title(painter, trect, db, book_id)
            else:
                if self.animating is not None and self.animating.row() == index.row():
                    cdata = cdata.scaled(cdata.size() * self._animated_size)
                dpr = cdata.devicePixelRatio()
                cw, ch = int(cdata.width() / dpr), int(cdata.height() / dpr)
                dx = max(0, int((rect.width() - cw)/2.0))
                dy = max(0, int((rect.height() - ch)/2.0))
                right_adjust = dx
                rect.adjust(dx, dy, -dx, -dy)
                painter.drawPixmap(rect, cdata)
                if self.title_height != 0:
                    self.paint_title(painter, trect, db, book_id)
            if self.emblem_size > 0:
                return  # We dont draw embossed emblems as the ondevice/marked emblems are drawn in the gutter
            if marked:
                try:
                    p = self.marked_emblem
                except AttributeError:
                    p = self.marked_emblem = m.marked_icon.pixmap(48, 48)
                self.paint_embossed_emblem(p, painter, orect, right_adjust)

            if on_device:
                try:
                    p = self.on_device_emblem
                except AttributeError:
                    p = self.on_device_emblem = QIcon(I('ok.png')).pixmap(48, 48)
                self.paint_embossed_emblem(p, painter, orect, right_adjust, left=False)
        finally:
            painter.restore()

    def paint_title(self, painter, rect, db, book_id):
        painter.setRenderHint(QPainter.TextAntialiasing, True)
        title, is_stars = self.render_field(db, book_id)
        if is_stars:
            painter.setFont(self.rating_font)
        metrics = painter.fontMetrics()
        painter.setPen(self.highlight_color)
        painter.drawText(rect, Qt.AlignCenter|Qt.TextSingleLine,
                            metrics.elidedText(title, Qt.ElideRight, rect.width()))

    def paint_emblems(self, painter, rect, emblems):
        gutter = self.emblem_size + self.MARGIN
        grect = QRect(rect)
        gpos = self.gutter_position
        if gpos is self.TOP:
            grect.setBottom(grect.top() + gutter)
            rect.setTop(rect.top() + gutter)
        elif gpos is self.BOTTOM:
            grect.setTop(grect.bottom() - gutter + self.MARGIN)
            rect.setBottom(rect.bottom() - gutter)
        elif gpos is self.LEFT:
            grect.setRight(grect.left() + gutter)
            rect.setLeft(rect.left() + gutter)
        else:
            grect.setLeft(grect.right() - gutter + self.MARGIN)
            rect.setRight(rect.right() - gutter)
        horizontal = gpos in (self.TOP, self.BOTTOM)
        painter.save()
        painter.setClipRect(grect)
        try:
            for i, emblem in enumerate(emblems):
                delta = 0 if i == 0 else self.emblem_size + self.MARGIN
                grect.moveLeft(grect.left() + delta) if horizontal else grect.moveTop(grect.top() + delta)
                rect = QRect(grect)
                rect.setWidth(int(emblem.width() / emblem.devicePixelRatio())), rect.setHeight(int(emblem.height() / emblem.devicePixelRatio()))
                painter.drawPixmap(rect, emblem)
        finally:
            painter.restore()

    def paint_embossed_emblem(self, pixmap, painter, orect, right_adjust, left=True):
        drect = QRect(orect)
        pw = int(pixmap.width() / pixmap.devicePixelRatio())
        ph = int(pixmap.height() / pixmap.devicePixelRatio())
        if left:
            drect.setLeft(drect.left() + right_adjust)
            drect.setRight(drect.left() + pw)
        else:
            drect.setRight(drect.right() - right_adjust)
            drect.setLeft(drect.right() - pw + 1)
        drect.setBottom(drect.bottom() - self.title_height)
        drect.setTop(drect.bottom() - ph)
        painter.drawPixmap(drect, pixmap)

    @pyqtSlot(QHelpEvent, QAbstractItemView, QStyleOptionViewItem, QModelIndex, result=bool)
    def helpEvent(self, event, view, option, index):
        if event is not None and view is not None and event.type() == QEvent.ToolTip:
            try:
                db = index.model().db
            except AttributeError:
                return False
            try:
                book_id = db.id(index.row())
            except (ValueError, IndexError, KeyError):
                return False
            db = db.new_api
            device_connected = self.parent().gui.device_connected
            on_device = device_connected is not None and db.field_for('ondevice', book_id)
            p = prepare_string_for_xml
            title = db.field_for('title', book_id)
            authors = db.field_for('authors', book_id)
            if title and authors:
                title = '<b>%s</b>' % ('<br>'.join(wrap(p(title), 120)))
                authors = '<br>'.join(wrap(p(' & '.join(authors)), 120))
                tt = '%s<br><br>%s' % (title, authors)
                series = db.field_for('series', book_id)
                if series:
                    use_roman_numbers=config['use_roman_numerals_for_series_number']
                    val = _('Book %(sidx)s of <span class="series_name">%(series)s</span>')%dict(
                        sidx=fmt_sidx(db.field_for('series_index', book_id), use_roman=use_roman_numbers),
                        series=p(series))
                    tt += '<br><br>' + val
                if on_device:
                    val = _('This book is on the device in %s') % on_device
                    tt += '<br><br>' + val
                QToolTip.showText(event.globalPos(), tt, view)
                return True
        return False

# }}}


# The View {{{

@setup_dnd_interface
class GridView(QListView):

    update_item = pyqtSignal(object)
    files_dropped = pyqtSignal(object)
    books_dropped = pyqtSignal(object)

    def __init__(self, parent):
        QListView.__init__(self, parent)
        self._ncols = None
        self.gesture_manager = GestureManager(self)
        setup_dnd_interface(self)
        self.setUniformItemSizes(True)
        self.setWrapping(True)
        self.setFlow(self.LeftToRight)
        # We cannot set layout mode to batched, because that breaks
        # restore_vpos()
        # self.setLayoutMode(self.Batched)
        self.setResizeMode(self.Adjust)
        self.setSelectionMode(self.ExtendedSelection)
        self.setVerticalScrollMode(self.ScrollPerPixel)
        self.delegate = CoverDelegate(self)
        self.delegate.animation.valueChanged.connect(self.animation_value_changed)
        self.delegate.animation.finished.connect(self.animation_done)
        self.setItemDelegate(self.delegate)
        self.setSpacing(self.delegate.spacing)
        self.set_color()
        self.ignore_render_requests = Event()
        dpr = self.device_pixel_ratio
        self.thumbnail_cache = ThumbnailCache(max_size=gprefs['cover_grid_disk_cache_size'],
            thumbnail_size=(int(dpr * self.delegate.cover_size.width()), int(dpr * self.delegate.cover_size.height())))
        self.render_thread = None
        self.update_item.connect(self.re_render, type=Qt.QueuedConnection)
        self.doubleClicked.connect(self.double_clicked)
        self.setCursor(Qt.PointingHandCursor)
        self.gui = parent
        self.context_menu = None
        self.update_timer = QTimer(self)
        self.update_timer.setInterval(200)
        self.update_timer.timeout.connect(self.update_viewport)
        self.update_timer.setSingleShot(True)
        self.resize_timer = t = QTimer(self)
        t.setInterval(200), t.setSingleShot(True)
        t.timeout.connect(self.update_memory_cover_cache_size)

    def viewportEvent(self, ev):
        try:
            ret = self.gesture_manager.handle_event(ev)
        except AttributeError:
            ret = None
        if ret is not None:
            return ret
        return QListView.viewportEvent(self, ev)

    @property
    def device_pixel_ratio(self):
        try:
            return self.devicePixelRatioF()
        except AttributeError:
            return self.devicePixelRatio()

    @property
    def first_visible_row(self):
        geom = self.viewport().geometry()
        for y in range(geom.top(), (self.spacing()*2) + geom.top(), 5):
            for x in range(geom.left(), (self.spacing()*2) + geom.left(), 5):
                ans = self.indexAt(QPoint(x, y)).row()
                if ans > -1:
                    return ans

    @property
    def last_visible_row(self):
        geom = self.viewport().geometry()
        for y in range(geom.bottom(), geom.bottom() - 2 * self.spacing(), -5):
            for x in range(geom.left(), (self.spacing()*2) + geom.left(), 5):
                ans = self.indexAt(QPoint(x, y)).row()
                if ans > -1:
                    item_width = self.delegate.item_size.width() + 2*self.spacing()
                    return ans + (geom.width() // item_width)

    def update_viewport(self):
        self.ignore_render_requests.clear()
        self.update_timer.stop()
        m = self.model()
        for r in range(self.first_visible_row or 0, self.last_visible_row or (m.count() - 1)):
            self.update(m.index(r, 0))

    def start_view_animation(self, index):
        d = self.delegate
        if d.animating is None and not config['disable_animations']:
            d.animating = index
            d.animation.start()

    def double_clicked(self, index):
        self.start_view_animation(index)
        if tweaks['doubleclick_on_library_view'] == 'open_viewer':
            self.gui.iactions['View'].view_triggered(index)
        elif tweaks['doubleclick_on_library_view'] in {'edit_metadata', 'edit_cell'}:
            self.gui.iactions['Edit Metadata'].edit_metadata(False, False)

    def animation_value_changed(self, value):
        if self.delegate.animating is not None:
            self.update(self.delegate.animating)

    def animation_done(self):
        if self.delegate.animating is not None:
            idx = self.delegate.animating
            self.delegate.animating = None
            self.update(idx)

    def set_color(self):
        r, g, b = gprefs['cover_grid_color']
        tex = gprefs['cover_grid_texture']
        pal = self.palette()
        pal.setColor(pal.Base, QColor(r, g, b))
        self.setPalette(pal)
        ss = ''
        if tex:
            from calibre.gui2.preferences.texture_chooser import texture_path
            path = texture_path(tex)
            if path:
                path = os.path.abspath(path).replace(os.sep, '/')
                ss += 'background-image: url({});'.format(path)
                ss += 'background-attachment: fixed;'
                pm = QPixmap(path)
                if not pm.isNull():
                    val = pm.scaled(1, 1).toImage().pixel(0, 0)
                    r, g, b = qRed(val), qGreen(val), qBlue(val)
        dark = max(r, g, b) < 115
        col = '#eee' if dark else '#111'
        ss += 'color: {};'.format(col)
        self.delegate.highlight_color = QColor(col)
        self.setStyleSheet('QListView {{ {} }}'.format(ss))

    def refresh_settings(self):
        size_changed = (
            gprefs['cover_grid_width'] != self.delegate.original_width or gprefs['cover_grid_height'] != self.delegate.original_height
        )
        if (size_changed or gprefs[
            'cover_grid_show_title'] != self.delegate.original_show_title or gprefs[
                'show_emblems'] != self.delegate.original_show_emblems or gprefs[
                    'emblem_size'] != self.delegate.orginal_emblem_size or gprefs[
                        'emblem_position'] != self.delegate.orginal_emblem_position):
            self.delegate.set_dimensions()
            self.setSpacing(self.delegate.spacing)
            if size_changed:
                self.delegate.cover_cache.clear()
        if gprefs['cover_grid_spacing'] != self.delegate.original_spacing:
            self.delegate.calculate_spacing()
            self.setSpacing(self.delegate.spacing)
        self.set_color()
        self.set_thumbnail_cache_image_size()
        cs = gprefs['cover_grid_disk_cache_size']
        if (cs*(1024**2)) != self.thumbnail_cache.max_size:
            self.thumbnail_cache.set_size(cs)
        self.update_memory_cover_cache_size()

    def set_thumbnail_cache_image_size(self):
        dpr = self.device_pixel_ratio
        self.thumbnail_cache.set_thumbnail_size(
            int(dpr * self.delegate.cover_size.width()), int(dpr*self.delegate.cover_size.height()))

    def resizeEvent(self, ev):
        self._ncols = None
        self.resize_timer.start()
        return QListView.resizeEvent(self, ev)

    def update_memory_cover_cache_size(self):
        try:
            sz = self.delegate.item_size
        except AttributeError:
            return
        rows, cols = self.width() // sz.width(), self.height() // sz.height()
        num = (rows + 1) * (cols + 1)
        limit = max(100, num * max(2, gprefs['cover_grid_cache_size_multiple']))
        if limit != self.delegate.cover_cache.limit:
            self.delegate.cover_cache.set_limit(limit)

    def shown(self):
        self.update_memory_cover_cache_size()
        if self.render_thread is None:
            self.thumbnail_cache.set_database(self.gui.current_db)
            self.render_thread = Thread(target=self.render_covers)
            self.render_thread.daemon = True
            self.render_thread.start()

    def render_covers(self):
        q = self.delegate.render_queue
        while True:
            book_id = q.get()
            try:
                if book_id is None:
                    return
                if self.ignore_render_requests.is_set():
                    continue
                try:
                    self.render_cover(book_id)
                except:
                    import traceback
                    traceback.print_exc()
            finally:
                q.task_done()

    def render_cover(self, book_id):
        if self.ignore_render_requests.is_set():
            return
        dpr = self.device_pixel_ratio
        page_width = int(dpr * self.delegate.cover_size.width())
        page_height = int(dpr * self.delegate.cover_size.height())
        tcdata, timestamp = self.thumbnail_cache[book_id]
        use_cache = False
        if timestamp is None:
            # Not in cache
            has_cover, cdata, timestamp = self.model().db.new_api.cover_or_cache(book_id, 0)
        else:
            has_cover, cdata, timestamp = self.model().db.new_api.cover_or_cache(book_id, timestamp)
            if has_cover and cdata is None:
                # The cached cover is fresh
                cdata = tcdata
                use_cache = True

        if has_cover:
            p = QImage()
            p.loadFromData(cdata, CACHE_FORMAT if cdata is tcdata else 'JPEG')
            p.setDevicePixelRatio(dpr)
            if p.isNull() and cdata is tcdata:
                # Invalid image in cache
                self.thumbnail_cache.invalidate((book_id,))
                self.update_item.emit(book_id)
                return
            cdata = None if p.isNull() else p
            if not use_cache:  # cache is stale
                if cdata is not None:
                    width, height = p.width(), p.height()
                    scaled, nwidth, nheight = fit_image(
                        width, height, page_width, page_height)
                    if scaled:
                        if self.ignore_render_requests.is_set():
                            return
                        p = p.scaled(nwidth, nheight, Qt.IgnoreAspectRatio, Qt.SmoothTransformation)
                        p.setDevicePixelRatio(dpr)
                    cdata = p
                # update cache
                if cdata is None:
                    self.thumbnail_cache.invalidate((book_id,))
                else:
                    try:
                        self.thumbnail_cache.insert(book_id, timestamp, image_to_data(cdata))
                    except EncodeError as err:
                        self.thumbnail_cache.invalidate((book_id,))
                        prints(err)
                    except Exception:
                        import traceback
                        traceback.print_exc()
        elif tcdata is not None:
            # Cover was removed, but it exists in cache, remove from cache
            self.thumbnail_cache.invalidate((book_id,))
        self.delegate.cover_cache.set(book_id, cdata)
        self.update_item.emit(book_id)

    def re_render(self, book_id):
        self.delegate.cover_cache.clear_staging()
        m = self.model()
        try:
            index = m.db.row(book_id)
        except (IndexError, ValueError, KeyError):
            return
        self.update(m.index(index, 0))

    def shutdown(self):
        self.ignore_render_requests.set()
        self.delegate.render_queue.put(None)
        self.thumbnail_cache.shutdown()

    def set_database(self, newdb, stage=0):
        if stage == 0:
            self.ignore_render_requests.set()
            try:
                for x in (self.delegate.cover_cache, self.thumbnail_cache):
                    self.model().db.new_api.remove_cover_cache(x)
            except AttributeError:
                pass  # db is None
            for x in (self.delegate.cover_cache, self.thumbnail_cache):
                newdb.new_api.add_cover_cache(x)
            try:
                # Use a timeout so that if, for some reason, the render thread
                # gets stuck, we dont deadlock, future covers wont get
                # rendered, but this is better than a deadlock
                join_with_timeout(self.delegate.render_queue)
            except RuntimeError:
                print('Cover rendering thread is stuck!')
            finally:
                self.ignore_render_requests.clear()
        else:
            self.delegate.cover_cache.clear()

    def select_rows(self, rows):
        sel = QItemSelection()
        sm = self.selectionModel()
        m = self.model()
        # Create a range based selector for each set of contiguous rows
        # as supplying selectors for each individual row causes very poor
        # performance if a large number of rows has to be selected.
        for k, g in itertools.groupby(enumerate(rows), lambda i_x:i_x[0]-i_x[1]):
            group = list(map(operator.itemgetter(1), g))
            sel.merge(QItemSelection(m.index(min(group), 0), m.index(max(group), 0)), sm.Select)
        sm.select(sel, sm.ClearAndSelect)

    def selectAll(self):
        # We re-implement this to ensure that only indexes from column 0 are
        # selected. The base class implementation selects all columns. This
        # causes problems with selection syncing, see
        # https://bugs.launchpad.net/bugs/1236348
        m = self.model()
        sm = self.selectionModel()
        sel = QItemSelection(m.index(0, 0), m.index(m.rowCount(QModelIndex())-1, 0))
        sm.select(sel, sm.ClearAndSelect)

    def set_current_row(self, row):
        sm = self.selectionModel()
        sm.setCurrentIndex(self.model().index(row, 0), sm.NoUpdate)

    def set_context_menu(self, menu):
        self.context_menu = menu

    def contextMenuEvent(self, event):
        if self.context_menu is None:
            return
        from calibre.gui2.main_window import clone_menu
        m = clone_menu(self.context_menu) if islinux else self.context_menu
        m.popup(event.globalPos())
        event.accept()

    def get_selected_ids(self):
        m = self.model()
        return [m.id(i) for i in self.selectionModel().selectedIndexes()]

    def restore_vpos(self, vpos):
        self.verticalScrollBar().setValue(vpos)

    def restore_hpos(self, hpos):
        pass

    def handle_mouse_press_event(self, ev):
        if QApplication.keyboardModifiers() & Qt.ShiftModifier:
            # Shift-Click in QListView is broken. It selects extra items in
            # various circumstances, for example, click on some item in the
            # middle of a row then click on an item in the next row, all items
            # in the first row will be selected instead of only items after the
            # middle item.
            index = self.indexAt(ev.pos())
            if not index.isValid():
                return
            ci = self.currentIndex()
            sm = self.selectionModel()
            sm.setCurrentIndex(index, sm.NoUpdate)
            if not ci.isValid():
                return
            if not sm.hasSelection():
                sm.select(index, sm.ClearAndSelect)
                return
            cr = ci.row()
            tgt = index.row()
            top = self.model().index(min(cr, tgt), 0)
            bottom = self.model().index(max(cr, tgt), 0)
            sm.select(QItemSelection(top, bottom), sm.Select)
        else:
            return QListView.mousePressEvent(self, ev)

    def indices_for_merge(self, resolved=True):
        return self.selectionModel().selectedIndexes()

    def number_of_columns(self):
        # Number of columns currently visible in the grid
        if self._ncols is None:
            dpr = self.device_pixel_ratio
            width = int(dpr * self.delegate.cover_size.width())
            height = int(dpr * self.delegate.cover_size.height())
            step = max(10, self.spacing())
            for y in range(step, 2 * height, step):
                for x in range(step, 2 * width, step):
                    i = self.indexAt(QPoint(x, y))
                    if i.isValid():
                        for x in range(self.viewport().width() - step, self.viewport().width() - width, -step):
                            j = self.indexAt(QPoint(x, y))
                            if j.isValid():
                                self._ncols = j.row() - i.row() + 1
                                return self._ncols
        return self._ncols

    def keyPressEvent(self, ev):
        if handle_enter_press(self, ev, self.start_view_animation, False):
            return
        k = ev.key()
        if ev.modifiers() & Qt.ShiftModifier and k in (Qt.Key_Left, Qt.Key_Right, Qt.Key_Up, Qt.Key_Down):
            ci = self.currentIndex()
            if not ci.isValid():
                return
            c = ci.row()
            ncols = self.number_of_columns() or 1
            delta = {Qt.Key_Left: -1, Qt.Key_Right: 1, Qt.Key_Up: -ncols, Qt.Key_Down: ncols}[k]
            n = max(0, min(c + delta, self.model().rowCount(None) - 1))
            if n == c:
                return
            sm = self.selectionModel()
            rows = {i.row() for i in sm.selectedIndexes()}
            if rows:
                mi, ma = min(rows), max(rows)
                end = mi if c == ma else ma if c == mi else c
            else:
                end = c
            top = self.model().index(min(n, end), 0)
            bottom = self.model().index(max(n, end), 0)
            sm.select(QItemSelection(top, bottom), sm.ClearAndSelect)
            sm.setCurrentIndex(self.model().index(n, 0), sm.NoUpdate)
        else:
            return QListView.keyPressEvent(self, ev)

    @property
    def current_book(self):
        ci = self.currentIndex()
        if ci.isValid():
            try:
                return self.model().db.data.index_to_id(ci.row())
            except (IndexError, ValueError, KeyError, TypeError, AttributeError):
                pass

    def current_book_state(self):
        return self.current_book

    def restore_current_book_state(self, state):
        book_id = state
        self.setFocus(Qt.OtherFocusReason)
        try:
            row = self.model().db.data.id_to_index(book_id)
        except (IndexError, ValueError, KeyError, TypeError, AttributeError):
            return
        self.set_current_row(row)
        self.select_rows((row,))
        self.scrollTo(self.model().index(row, 0), self.PositionAtCenter)

    def marked_changed(self, old_marked, current_marked):
        changed = old_marked | current_marked
        m = self.model()
        for book_id in changed:
            try:
                self.update(m.index(m.db.data.id_to_index(book_id), 0))
            except ValueError:
                pass

    def moveCursor(self, action, modifiers):
        index = QListView.moveCursor(self, action, modifiers)
        if action in (QListView.MoveLeft, QListView.MoveRight) and index.isValid():
            ci = self.currentIndex()
            if ci.isValid() and index.row() == ci.row():
                nr = index.row() + (1 if action == QListView.MoveRight else -1)
                if 0 <= nr < self.model().rowCount(QModelIndex()):
                    index = self.model().index(nr, 0)
        return index

    def selectionCommand(self, index, event):
        if event and event.type() == event.KeyPress and event.key() in (Qt.Key_Home, Qt.Key_End) and event.modifiers() & Qt.CTRL:
            return QItemSelectionModel.ClearAndSelect | QItemSelectionModel.Rows
        return super(GridView, self).selectionCommand(index, event)

    def wheelEvent(self, ev):
        if ev.phase() not in (Qt.ScrollUpdate, 0):
            return
        number_of_pixels = ev.pixelDelta()
        number_of_degrees = ev.angleDelta() / 8.0
        b = self.verticalScrollBar()
        if number_of_pixels.isNull() or islinux:
            # pixelDelta() is broken on linux with wheel mice
            dy = number_of_degrees.y() / 15.0
            # Scroll by approximately half a row
            dy = int(math.ceil((dy) * b.singleStep() / 2.0))
        else:
            dy = number_of_pixels.y()
        if abs(dy) > 0:
            b.setValue(b.value() - dy)

    def paintEvent(self, ev):
        dpr = self.device_pixel_ratio
        page_width = int(dpr * self.delegate.cover_size.width())
        page_height = int(dpr * self.delegate.cover_size.height())
        size_changed = self.thumbnail_cache.set_thumbnail_size(page_width, page_height)
        if size_changed:
            self.delegate.cover_cache.clear()

        return super(GridView, self).paintEvent(ev)

# }}}
